This invention relates to mobile communication and as an example refers to the currently discussed and developed Long-Term Evolution standard (LTE), which features, among others, a Multimedia Broadcast-Multicast Service (MBMS). Service of MBMS may comprise for example, audio, video, still images, or any other type of media or combined media types such as mobile-TV or the like, without limiting the applicability of the present invention, whether to the media type or types or to the service as such.
In its previous release, i.e. LTE Rel-9, those standards include a basic MBMS functionality, of pure broadcast-mode MBMS transmission. The subsequent release, i.e. LTE Rel-10 has further developed such MBMS service in various aspects.
That is, in brief, responsive to a network-broadcast request, terminals (such as user equipments UEs) which are in a connected state in terms of radio resource control (RRC), i.e. in RRC_Connected mode, indicate if they are interested in receiving such services.
MBMS reception is possible for a terminal UE just as well in another mode or state known as RRC_Idle. Note that while MBMS service is used in singular here, it is understood that plural services may be covered. Many terminals UE which are in state RRC_Idle are present in each tracking area. A tracking area generally denotes the area and/or one or more cells where, as opposed to an exact cell, a UE in RRC_Idle is known to reside or to camp.
UE mobility for UE's in IDLE mode is generally to a certain extent based on the UE decision rather than on a network decision as in a handover procedure. Thus, the network has only little control over IDLE mode UE mobility due to a lacking RRC connection.
As a UE, when in IDLE mode, is not RRC connected to the network yet, balancing a network load originating by the IDLE mode UE′ is not as critical as for balancing a network load due to UE's in CONNECTED mode. However as IDLE mode UEs will make the connection to the network on the layer (or frequency) where it is camped on, in the bigger meaning, IDLE mode UE load balancing is related to CONNECTED mode UE load balancing. At the latest in the event that an IDLE mode UE transits to CONNECTED mode, the network load balance is likely to be affected by the layers on which the IDLE mode UE was camped on. Namely, when paged, the IDLE mode UE will respond on the layer on which it was paged and establish an RRC connection on that layer.
Thus it is important that network can control IDLE mode mobility and UE camping is predictable. (“Mobility” in this context rather refers to inter-frequency/inter-layer mobility rather than to spatial mobility.) Also, due to the operator policy, operators may want to keep the UEs more in certain frequency or RAT. And for the IDLE mode UE distribution, priority per frequency and RAT is included in a system information block SIB. Therefore, it is beneficial that UE follows the priority which the network provides as broadcasted information in the SIB.
However, for MBMS reception in Rel-11, it is necessary for the network to allow UE to violate (or diverge from) the current reselection rule. However, if so, the network will lose control and load balancing in for IDLE mode UE's and also for CONNECTED mode UE's load balancing control will be lost at the latest once IDLE UE's transit to CONNECTED mode. Also, as UE behaviours may be different from UE to UE or from user to user, there is no longer a predictable behaviour of the UEs within the network.
Therefore, it is an object of the present invention to propose improvements in scenarios for service reception for terminals in IDLE mode.